Cast iron, this metallic material, with its unique physical and mechanical properties, is widely used in multiple fields. There are numerous types, and the common ones can be classified into six types, each with its specific application scenarios. Next, we will delve into the unique uses and applications of these six types of cast iron and the three major types of cast steel.

Gray cast iron.

Its carbon content is relatively high, ranging from 2.7% to 4.0%. The carbon mainly exists in the form of flake graphite, causing the fracture surface to appear gray. Therefore, it is simply called gray iron. The melting point of this type of cast iron is relatively low, ranging from 1145 to 1250℃, and the shrinkage during solidification is small. Although its compressive strength and hardness are close to those of carbon steel, it has good shock absorption performance. Therefore, gray cast iron is often used to manufacture structural components such as machine tool beds, cylinders and boxes.

② White cast iron.

The carbon and silicon content of this type of cast iron is relatively low. The carbon mainly exists in the form of cementite, which makes its fracture surface appear silvery white. Due to the large shrinkage during solidification, white cast iron is prone to shrinkage cavities and cracks. Although it has high hardness, it is also brittle and cannot withstand impact loads. Therefore, white cast iron is often used as the blank for malleable cast iron and for making wear-resistant components.

③ Malleable cast iron.

It is obtained by annealing white cast iron, with graphite distributed in a flocculent form, and thus is simply called ductile iron. The microstructure and properties of this cast iron are uniform. It is not only wear-resistant but also has good plasticity and toughness. Therefore, malleable cast iron is often used to manufacture parts with complex shapes that need to withstand strong dynamic loads.

④ Ductile iron.

It is obtained by subjecting gray cast iron molten iron to spheroidizing treatment, in which the graphite precipitated is spherical, and thus it is simply called ductile iron. Compared with ordinary gray cast iron, ductile iron has higher strength, better toughness and plasticity. This makes it an ideal choice for manufacturing internal combustion engines, automotive parts and agricultural machinery, etc.

⑤ Vermicular graphite cast iron.

This type of cast iron is obtained by subjecting the molten gray cast iron to creep treatment, and the graphite precipitated from it is in a worm-like form. Its mechanical properties are similar to those of ductile iron, and at the same time, its casting performance lies between that of gray cast iron and ductile iron. Therefore, vermicular graphite cast iron is often used to manufacture automotive parts.

⑥ Alloy cast iron.

This kind of cast iron is obtained by adding an appropriate amount of alloying elements (such as silicon, manganese, phosphorus, nickel, chromium, etc.) to ordinary cast iron. The addition of alloying elements will change the matrix structure of cast iron, thereby endowing it with properties such as heat resistance, wear resistance, corrosion resistance, low-temperature resistance or non-magnetism. This makes alloy cast iron widely used in the manufacturing of components for mining, chemical machinery, instruments and meters, etc.

In addition, cast steel is also an important casting alloy, which is mainly used for pouring castings. Cast steel can be classified into three types: cast carbon steel, cast low alloy steel and cast special steel, and is widely used in mechanical manufacturing, petrochemicals and other fields.